In high power light emitting diode (LED) lighting applications, it is necessary to drive multiple LEDs with substantially equal current. This can be accomplished by connecting all of the LEDs in series. However, based on the number of LEDs in a given application, this type of configuration can result in excessively high voltages. For example, thirty series connected LEDs may develop a voltage in excess of 100 volts. One solution to mitigate the utilization of excessively high voltages is to divide the LEDs into groups of LED strings consisting of a number of series connected LEDs, such that each LED string will develop a safe voltage when driven with a required current. For example, the 30 LEDs mentioned above may be divided into three strings of 10 LEDs with a voltage of about 34 volts per string.
To facilitate current regulation across the groups of LED strings, each LED string can be connected to a common low voltage source with each LED string being regulated by a respective linear or switching current regulator. However, this solution is expensive because of the added regulators and the current balance of the strings is less than perfect due to the tolerances and offsets associated with separate current loops. Furthermore, the added regulators will reduce the system efficiency and may produce additional electromagnetic interference (EMI) that will contribute to further increased costs and increased efficiency erosion.